1.89 * 10^12 is a number written in scientific notation. To write a number in scientific notation, you write a number that is 1 or greater and less than 10, and then multiply it by 10 raised to an integer.
1.89 is the number from 1 to under 10.
12 is the integer exponent of 10.
The calculator writes 1.89 * 10^12, the number in scientific notation, as 1.89E12.
Again, 1.89 is the number from 1 to under 10, and 12 is the exponent. The E shows that the number after it is the exponent.
To write 1.89 * 10^-12, the calculator would write 1.89E-12.
The E stands for the exponent of 10 in scientific notation.